1. Field of the Invention
The present invention relates to a voltage adjuster for an AC (alternating-current) generator for a vehicle that is mounted in a vehicle or the like and controls an output voltage, and particularly to a cooling structure of the voltage adjuster.
2. Description of the Related Art
There is known a conventional voltage adjuster for use in an AC generator for a vehicle in which cooling air is made to flow through a ventilation path between cooling fins of a heat sink for the voltage adjuster over the whole length in the radial direction to efficiently absorb heat generation under use, thereby suppressing deterioration of cooling performance (see JP-A-2007-336695, pp 3-4, FIGS. 6 and 7, for example). A cooling plate having plural cooling fins extending in parallel can be obtained at low cost by extruding or drawing aluminum material or the like so as to form the cooling fins in the same sectional shape.
There is also known another conventional voltage adjuster in which a blind alley type ventilation path is discontinuously formed in a ventilation direction by a thin-walled aluminum plate, that is, a base portion adhesively fixed to a control circuit portion and a heat radiation portion having a substantially U-shaped transverse section in the ventilation direction, so that blocking caused by foreign materials pinched in a continuous ventilation path can be suppressed (see JP-A-2003-244913, pp 2-5, FIGS. 3 and 5, for example).
In the construction using the conventional cooling plate disclosed in JP-A-336695, sufficient cooling air flows through the ventilation path between the heat sink fins, however, only the longitudinal side surfaces of the fins are used, that is, it is not sure that how degree the end surfaces of the fins (the cut surfaces of the fins in the extrusion process) contribute to cooling.
Furthermore, in the other example in which the ventilation path is discontinuously formed in the ventilation direction disclosed in JP-A-2003-244913, the side surfaces of individual heat radiation portions as the end surfaces of the fins are exposed in the ventilation direction, however, the heat-radiation effect thereof is based on the small thickness. Furthermore, in order to obtain this construction, a thin-walled aluminum plate different from a heat sink is required to be subjected to press molding, and thus there is a problem that addition and change of the facilities, steps, etc. of the press molding are indispensable.